There are various types of observations that JWST proposers can request. Primary observations are classically targeted observations, which determine the telescope pointing, orientation, and scheduling. There other types of observations that require additional considerations in planning and scheduling. These include parallel observations (coordinated or as pure parallel), time constrained or critical observations, observations of Solar System targets, target-of-opportunity observations (disruptive or non-disruptive), follow-up of targets from JWST pre-imaging, and observations of targets that have not yet been discovered or identified. 

Many of these observation types are described with roadmaps and examples on Methods and Roadmaps.

In general, observing programs that require the use of Special Requirements, especially those that affect timing and schedulability of observations, must include a scientific justification of why the Special Requirements are necessary.

Next: Coordinated and Pure-Parallel Observations